earthing and bonding

International Telecommunication Union

Technical Session, ProtectionBuenos Aires, 12/04/2010

ITU-T Study Group 05

EarthingEarthing and bondingand bonding

Claude Monney

Switzerland

ITU-TStudy Group 05

Introduction

Earthing and especially bonding are the pre-

requisite for the protection of equipments. It

insures that no dangerous voltages (both for the

equipment and for people) appear between ports.

TECHNICAL SESSION – PROTECTION - BUENOS AIRES 12.04.2010

ITU-TStudy Group 05

Relationship between earthing, bonding and surges

ELP: external lightning protection

Conducteddisturbances

Radiateddisturbances

Earthpotential rise

ELP

EN

MBN SPD

SPD: surge protection devices

EN: earthing network

MBN : Mesh bonding

network


ITU-TStudy Group 05

Relevant Recommendations

K.27: Bonding configurations and earthing

inside a telecommunication building

(1996)

K.35: Bonding configurations and earthing at

remote electronic sites (1996)

K.56: Protection of radio base stations against

lightning discharges (2010)

K.66: Protection of customer premises from

overvoltages (2004)

Earthing and Bonding handbook (2003)

IEC 60364-4-44: Protection against voltage

disturbances and electromagnetic

disturbances (2007)TECHNICAL SESSION – PROTECTION - BUENOS AIRES 12.04.2010

ITU-TStudy Group 05

Differences between earthing and bonding

Though both terms are commonly used together,

a clear distinction should be done

Bonding: Electrical connection putting

various exposed conductive parts and extraneous

conductive parts at a substantially equal potential.

Earthing: Connecting the bonding network

or bonding conductor to an earth electrode to

provide a defined path for the current flow and

reduce potential differences


ITU-TStudy Group 05

PE

T0506060-92/d05

L1 L2 L3 N PE

PE

Floor

Support column of the building

Reinforcement

Bonding ring conductorSystem block 1

Mesh-BN equipment

Interconnection

Bonding mat

Interconnected

reinforcement

Mesh-BN

equipment

48 V dc

service panel

Frame of dc

powerplant

Plumbing

Aircon

AC distribution

System block 2

mesh-BN equipment

Main earthing terminal

To foundation

reinforcement/ring

conductor

To earth

electrode

Telecom

cables

Basement

Lower floor

Floor n

Floor n+1

DC return conductor (+48 V)

Interconnected reinforcement

and building steel

Intra-system cabling

Shielded inter-system cabling

Bonding conductor

FIGURE B.1/K.27

Mesh-BN installation inside a telecommunication building

Bonding ring conductor

(recommended)

Connection of cable shield

to the rack is recommendedDifferences between earthing and bonding Bonding network

Bonding conductor

Earthing conductor


ITU-TStudy Group 05

Bonding networks

• Bonding is key to survive to overvoltages and overcurrents

• As shown in the film, earthing is secondary.

There are mainly 2 bonding networks’ families

oIn addition, one can either link all connections together or

isolate them from the structure

T0506760-95/d01

Star topology Mesh topology

Rack, equipment, module

Bonding conductor

FIGURE 1/K.27

Bonding network configurations forming a system block


ITU-TStudy Group 05

Bonding networks

Not applicable

Star -IBN Mesh-IBNSPCWSPCW

may be ofzero length

Mesh-BN

BN

CBN

IBN

SPCW

Bonding Network

Common Bonding Network

Isolated Bonding Network

Single Point Connection Window

Multip

le p

oin

tS

ingle

poin

t

Star configuration Mesh configuration

Rack, equipment, module, etc.

Bonding conductor

Nearby elements of CBN

Connection to CBN

Inte

gra

tion o

f th

e B

N into

the C

BN

FIGURE 2/K.27

Connection of system block to the CBN

Preferred

solution


ITU-TStudy Group 05

Maintenance of bonding networks

o Small changes that occur in the CBN generally have only

a small effect on its shielding capability.

o Additional shielding may be obtained by introduction of

additional conductors (e.g. bonding conductors, cable

trays, and conduit). Such modifications are usually

straightforward.

o IBN systems are more difficult to maintain, because

craft-person activity is liable to result in inadvertent

interconnections between IBN and CBN, violating the

desired single point connection, and introducing surge

currents into the IBN.

o It is recommended that systematic verification be

performed on all bonding configurations and earthing

connections inside a telecommunications building.


ITU-TStudy Group 05

AC power distribution

o From an EMC perspective, TN-S systems should

be preferred

T0506990-96/d01

PE DC-return


Earthing network

PEPE

PEN

N

Output to indoor

mains installation (TN-S)

N

N

PEPE

PE DC-return


Earthing network

N

N

PEPE

PE DC-return


Earthing network

PE

Mode 1: TN-S/TN-S

ring conductor

Input from outdoor

mains distribution (TN-S)

NOTE – Mode 1 is obligatory if a separation transformer is dedicated to the building and the

TN-S system consequently originates at the transformer load side.

Mode 2: TN-C/TN-S

Output to indoor

mains installation (TN-S)

Input from outdoormains distribution (TN-C)

ring conductor

Mode 3: IT/IT or TT/TT

Output to indoor

mains installation (IT or TT)

Input from outdoor

mains distribution (IT or TT)

ring conductor

Outd

oor

main

s d

istr

ibution

Outd

oor

main

s d

istr

ibutio

nO

utd

oor

main

s d

istr

ibution

FIGURE 1/K.35

Arrangements for the transition from the outdoor mains distributionnetwork to the indoor mains


ITU-TStudy Group 05

TN-S inside the building


Bonding at

floor level

reduces

potential differences

ITU-TStudy Group 05

Earthing

The main functions of earthing are:

• Provide a safe path to the flow of surge current to

earth (e.g., from lightning)

• Reduce the current and voltage propagating along a

transmission line (e.g., a telecom cable)

• Reduce the voltage between the telecom line and

local earth

• Provide sufficient current for the tripping of circuit

breakers in case of a power to earth fault.


ITU-TStudy Group 05

Earthing

2) Ring electrode

3) Vertical rod

1) Armoured concrete

In the preference order


ITU-TStudy Group 05

Example for a small telecom center

2

3

T0507380-96/d02

1 1

Ring

bonding- bus

Equipment

frame

To earthing network

a.c. service

enclosure

Main

earthing

terminal

Earthing network

Supplementary

bonding-bus

1 Earthing conductor

2 Equipment bonding conductor

3 Protective conductor

FIGURE I.1/K.35

Example of bonding configurations and earthing of EEEs by use of ring bonding-bus12.04.2010 TECHNICAL SESSION – PROTECTION - BUENOS AIRES

ITU-TStudy Group 05

Example for a base station

12.04.2010 TECHNICAL SESSION – PROTECTION - BUENOS AIRES

ITU-TStudy Group 05

Overvoltage protection

o It isn’t possible to integrate live

conductors into the bonding network

o In order to limit the overvoltage to a

defined level, surge protection

devices are required


earthing and bonding

Documents

indoor mains

outdoor mains

technical

surge protection

ring conductor

bonding conductor

bonding network

base station